When process steam/heat in steam power plants is extracted, owing to leakages and losses of process steam/condensate, the water-steam circuit has to be made up by means of the continuous feeding in of makeup water. The makeup water is as a rule prepared but not degasified. For example, the makeup water contains dissolved foreign gases which have to be expelled again in a degasser of the steam power process. In order to increase the process efficiency, the makeup water has to be preheated before entry into the degasser.
At present, the makeup water is supplied, for example, to a conventional degasification device, directly into the degasser. This is technically simple and involves less cost, but is the most unfavorable variant in terms of energy.
In addition, the makeup water can be fed directly into a turbine condenser or into a low pressure preheater. This variant can, however, only be applied for relatively small quantities of makeup water.
FIG. 2 illustrates a further conventional system for feeding makeup water into a water-steam circuit. The condensate from a conventional condenser 201 is pumped into a container 204 by a conventional condensate pump 202. In addition, a mass flow m, of the makeup water is mixed in there by means of a conventional feed line 203. The water mixture is subsequently pumped into the conventional degasification device 209 by a further condensate pump 205 through conventional heating devices 206, 208 of the water-steam circuit. Since the water mixture is not degasified owing to the makeup water portion and therefore contains dissolved and corrosive media (for example oxygen), all the containers, lines and fittings, including the container 204 up to the conventional degasification device, have to be constructed from corrosion-free stainless steel. The water is fed to a conventional evaporator 207 downstream of the conventional degasification device 209.